1. Field of the Invention
The present invention relates to an LED package, an LED package mounting structure comprising an LED package mounted on a circuit board such as a printed circuit board, and a liquid crystal display comprising an LED package mounting structure.
2. Description of the Related Art
In recent years, LEDs are increasingly used as light sources of backlight units for liquid crystal displays of televisions and monitors. This current corresponds to the demands for improved efficiencies of liquid crystal displays, and by using LED light sources, the power consumption and thickness of television sets can be reduced than in conventional cold cathode fluorescent tubes. In particular, by realizing area control, which is controlling LEDs constituting the backlight unit by dividing them into a plurality of groups and controlling the luminance of the LEDs group by group depending on the content of the image, power consumption can be further lowered and high-resolution imaging is achieved.
Backlight systems of liquid crystal displays which allow area control are roughly divided into direct lighting systems and slim block systems. In the direct lighting system, a number of LED light sources are dispersedly disposed within a plane in such a manner that their optical axes are perpendicular to a liquid crystal panel, and the light rays are mixed by a diffuser which is disposed at a point some distance from the light sources to homogenize luminance. Meanwhile, a slim block system is so constituted that a plurality of combinations of a plurality of LEDs and a series of light guide plates are arranged within a plane two-dimensionally, and the LEDs are disposed beside the light guide plates in such a manner that their optical axes are parallel to the liquid crystal panel. A light ray emitted from a light source is, when it is incident from the side face of a light guide plate, totally reflected within the light guide plate, propagated, scattered by reflecting dots or other elements formed on the bottom face of the light guide plate, and is taken out at the top face of the light guide plate. Since the slim block system does not require a space to obtain uniform luminance distribution within the plane, as opposed to the direct lighting system, it can be formed more thinly.
When the slim block system is employed, in order to use a generic upward-lighting type surface mounted LED package (hereinafter referred to as a top-view type LED package) with which the optical axis is perpendicular to the mounting surface of the LED package, a relay board needs to be joined to a circuit board by soldering perpendicularly after LEDs are mounted on the relay board, or the relay board needs to fixed perpendicularly to a chassis and then wired with a connector or other parts. This increases the number of parts and assembly steps and thus increases the costs.
When the side-view type LED package is used, the LEDs are directly mounted on a circuit board such as a printed circuit board, and therefore the costs can be advantageously reduced.